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op amps for audio

Posted 23rd January 2012 at 06:36 AM by rjm

Douglas Self on op amps for audio, which I read before in slightly different form, on another web site somewhere, many years ago... today was a refresher course.

Excerpts from op amps in small signal audio design, by D. Self [Part 1, part 2, part 3, part 4].

I suppose I should get with the times and start using the LM4562 seeing as it is available in DIP8 now. (I had this memory that it was only SOIC, go figure...) Pity it's dual only. On the other hand, that leads to some neat ideas, like a compact version of the Sapphire amp for example, or the X-reg.

I am struck by how few choices we really have when it comes to practical op amps for audio in single DIP8 packages. There is the NE5534, TL071 and TL051, the OPA134, the OPA604, and OPA27, OPA627. Maybe the AD797 but I have yet to see the point. Given that the TL1071 and derivatives are outdated and replaced essentially by the OPA134, and given the excessive cost (and questionable sonic benefit) of the OPA627, and given the rather nondescript performance and suspect "black box" design of the OPA604, one is basically left with NE5534 for general work, OPA134 for high impedance, low input current applications (following volume controls) and the OPA27 for phono stages and low noise, low impedance work preferably in the inverting circuit topology.

For dual DIP8 packages, NE5532 or LM4562, and for FET input, OPA2134.
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  1. Old Comment
    dimkasta's Avatar
    So would you suggest OPA27 for vsps and phonoclone? (including reg?)
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    Posted 19th February 2012 at 12:08 PM by dimkasta dimkasta is offline
  2. Old Comment
    rjm's Avatar
    I think the take home message here is that you can't judge an op amp out of context. So much depends on input impedance, output loads, gain configuration, and power supply bypassing.

    The OP27 sounds really good in the Phonoclone, and based on the datasheets it is the optimal choice for that setting. The (non-inverting) VSPS is less clear, I would be inclined to experiment. For the Sapphire, which is also non-inverting and comparatively low gain, high input impedance, application, the NE5534 and OPA134 are clearly better.
    permalink
    Posted 25th February 2012 at 11:51 PM by rjm rjm is offline
 
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